[Physics] Clocks in relativity

[carmam at tiscali.co.uk]

No more debate with you Thomas. How can there be a sensible debate with a person who says that the moon coalescing with the Earth is acceptable, but derides the notion of a planet without one? And to boot calls it silly.Goodbye,Tom.



----Original Message----
From: thomas at flyingkettle.com
Date: 15/11/2016 11:17
To: <physics at tuks.nl>
Subj: [Physics] Clocks in relativity

On 15 Nov 2016 at 12:00, physics-request at tuks.nl wrote:

> We can dispense with the qualification "with reference to
> frame ??" can we not, as it it is well understood by
> anyone on this forum. 

No, we can't, because many people misunderstand the 
situation.

> > This behavior
> > is a brute fact.

> By using the phrase "this behaviour is a
> brute fact" do you mean it is physically real?

It depends what you mean by "physically real". Each one of 
two moving observers, when he looks at (considered in his 
own reference frame, of course) the clock of the other 
observer, sees that it is running slower than his clock. 
That is the brute fact. I don't know whether you would 
consider that fact to be "physically real" or not; but 
anyway, it's what is always actually observed in that 
situation. 

> Einstein  himself said (and I am not going to look it up
> to reference it) "It does not matter what type of clock
> is used."  

But obviously he meant, an accurate clock. If the clock is 
bad, and its running speed fluctuates widely, nothing 
whatever can be said about it. Of course. For example, if 
you use your heartbeat as a clock, you will not reach any 
physically meaningful results.

> The point I was making is that a light based clock
> (cesium / atomic) is not a supremely accurate clock, it
> is subject to errors, just the same as the pendulum
> clock. 

Not just the same. Very much less accurate. In fact, if you 
accept the modern SI definition of the second, which you 
must do, the cesium clock (when perfectly implemented) has 
no errors. The fact that two cesium clocks do not agree 
with one another exactly, implies that at least one of them 
is only imperfectly implemented. Probably only slightly 
imperfectly.

I repeat, in the context of a changing gravitational field 
(changing acceleration), a pendulum clock is a very poor 
clock.  

> Saying that the meridian passes the fixed star is bantering
> semantics.

No, it isn't, because rotation is absolute. The fixed stars 
definitely do not rotate around the earth!

> The rate of the meridian clock changes by the same 
> amount for the person at the top of the mountain and the
>  person at the bottom, so is unnoticeable to either and
> they are still in the same time frame.  

They are not in the same "time frame", whatever that means. 
The clock at the bottom of the mountain will run slow as 
compared to the clock at the top. Of course a person next 
to the clock at the bottom will notice nothing when looking 
at his own clock (and the same for a person at the top).

> Also we are here conducting a thought experiment, so we
> can find a planet without a moon, or simply assume that
> the moon does not exist. 

Again, this is irrelevant, indeed frankly silly.

Thomas Goodey
****************** 

But remember, please, the rules by which we live. 
We are not built to comprehend a lie. 
We can neither love, nor pity, nor forgive. 
If you make a slip in handling us you die.  

Rudyard Kipling, 'Secret of the Machines'


_______________________________________________
Physics mailing list
Physics at tuks.nl
http://mail.tuks.nl/cgi-bin/mailman/listinfo/physics



-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mail.tuks.nl/pipermail/physics/attachments/20161115/a9643519/attachment.html>